Abstract：There are three independent control degrees of freedom in dual active bridge DC-DC converters (DAB) with triple phase shift (TPS) control. The current stress in a DAB can be reduced by a reasonable combination of changes in the phase shift degrees of freedom. However, soft switching analyses show that the system efficiency is not necessarily optimized when the DAB current stress is optimized. This paper presents a performance comprehensive optimization method that considers both the current stress and the efficiency based on current stress optimization control. Firstly, a DAB loss model for TPS control is developed based on the switching combination laws. A commutation loop analysis is used to separately predict the on-state losses and switching losses of the semiconductor devices and the copper losses and iron losses of the magnetic component for any combination of switches. Then, an efficiency optimization weight is introduced to construct the optimal objective function balancing the current stress and efficiency. A two-dimensional traversal algorithm is then used to optimize the DAB working point. The DAB performance is compared to measurements when the current stress or efficiency is optimized separately. Proper selection of the weight increased the prototype efficiency when transmitting 6 kW by 0.83% with the current stress only increased by 0.5 A. Thus, this method effectively improves the system efficiency without substantially increasing the current stress.
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2019, Vol. 59 
